The trend in the circuit protection industry is currently toward complete circuit protection which is accomplished by the addition of supplemental protection apparatus to standard overcurrent protective devices, such as molded case circuit breakers. In the past, when such auxiliary protection apparatus or other circuit breaker accessories were combined with a standard circuit breaker, the accessories were usually custom-installed at the point of manufacture. The combined protective device, when later installed in the field, could not be externally accessed for inspection, replacement or repair without destroying the integrity of the circuit breaker U.S. Pat. No. 4,894,631 describes a molded case circuit breaker containing an actuator-accessory unit which provides a wide variety of circuit protection accessory options. This patent is incorporated herein for purposes of reference and should be reviewed for its description of the state-of-the-art of such circuit breakers and accessory devices.
U.S. Pat. No. 4,913,503 describes a reset mechanism for a lower ampere-rated circuit interrupter usually employed as a "branch" circuit interrupter within industrial power distribution systems downstream from a higher-rated "main" circuit interrupter. When actuator-accessory units are used within the higher-rated circuits, the actuator-accessory units are incapable of providing sufficient force per se, to overcome the holding force of the powerful operating mechanism springs. Additional trip force is provided by a supplemental tripping mechanism which interacts with the actuator-accessory unit through a sequential resetting arrangement to insure that the actuator-accessory unit becomes reset before the main operating mechanism is reset.
One purpose of this invention is to describe such a sequential resetting system that interfaces between the tripping mechanism and the actuator-accessory unit of a higher-rated molded case circuit interrupter to insure that the actuator-accessory unit becomes reset before the main operating mechanism.